Method for controlling a base station, and base station

ABSTRACT

A method for controlling a base station ( 100, 200 ), used in a cellular radio system employing a TDMA multiple access method and having terminals ( 41-45 ), sectors ( 51-55 ) and at least one base station ( 100, 200 ) which transmits one or more carriers, and which has a number of baseband parts ( 16, 25 ), and at least one transmitter/receiver unit ( 12, 22 ), and which is connected to the rest of the system by a digital transmission line ( 70 ) in which information is transmitted in timeslots. The timeslots are allocated as required to different carriers, the baseband parts ( 16, 25 ) are allocated as required to different sectors ( 51-55 ) and the timeslots are allocated to different carriers so that one carrier will have no more than 16 timeslots.

BACKGROUND OF THE INVENTION

The present invention relates to a method for controlling a basestation, used in a cellular radio system employing TDMA multiple accessmethod and comprising terminals, sectors and at least one base stationwhich transmits one or more carriers, and which comprises a number ofbaseband parts, and at least one transmitter/receiver unit, and which isconnected to the rest of the system by a digital transmission line inwhich information is transmitted in timeslots.

Prior art knows a Base Transceiver Station (i.e. BTS) of a cellularradio system, which transmits data to the radio path and which receivesdata from the radio path. The data stream received from the transmissionpath at the base station has been divided into frames that comprisetimeslots. The timeslots comprise, in digital form, data contained bythe different channels. The data in the timeslots of the frame have beenprocessed in a suitable way at the base station, and the processed datahave been allocated via the base station sections to subscriberterminals located in different parts in a sector of a cell in thecellular radio system. In the known solutions, channel allocation todifferent carriers and sectors has been determined by fixed timeslotallocation settings.

It has not, however, been easy to change the allocation settings ofchannels received at the base station because the allocation settingshave been fixed. As a consequence of the difficult changing of theallocation settings, it has not been possible to utilize thetransmission path capacity efficiently or flexibly enough. What was setforth above means that the data equipments on the transmission path havenot met quickly or efficiently enough the requirements of otherequipments using the transmission path. Allocation of channels intodifferent sectors in the prior art required changing the allocationsettings of transmission equipments in the base station, which wasdifficult and slow because the settings had to be changed manually. Itwas necessary to allocate timeslots from the transmission equipmentseven though the base station at that moment was not able to utilize theallocated timeslots. The costs have been added to by the requirement toallocate a lot of capacity in a base station in order to take intoaccount that the network is at times loaded heavily and unevenly. Ithas, however, proved to be difficult to change the channel configurationof the network so that the network would operate flexibly under allloads.

BRIEF SUMMARY OF THE INVENTION

It is consequently the object of the present invention to provide amethod by means of which the allocation of channels originating from thetransmission direction may be allocated to the radio path as flexiblyand efficiently as possible.

This object is achieved by means of a method of the type set, forth inthe introduction, characterized in that timeslots are allocated asrequired to different carriers, and that the baseband parts areallocated as required to the different sectors.

The invention further relates to a base station used in a cellular radiosystem employing TDMA multiple access method and comprising terminals,sectors, a transmission line and at least one base station Whichtransmits one or more carriers, and which comprises a number of basebandparts, and at least one transmitter/receiver unit, and which isconnected to the rest of the system by a digital transmission line inwhich information is transmitted in timeslots.

The receiver according to the invention is characterized by comprisingcontrol means for allocating the timeslots as required to differentcarriers, and for allocating the baseband parts to different sectors.

With the method according to the invention, reconfiguration of channelallocation settings, related to the known methods, may be avoided. Inthe method, the base station assigns the channels received in timeslotsat the base station in its transmission block, i.e. allocation means, toany of the carriers transmitted by the base station. This results inthat the method according to the invention contributes to a cellularradio network, particularly a GSM network, becoming more flexible andeasier to maintain.

The base station according to the invention also has a number ofadvantages. The base station assigns timeslots received at theallocation means of the base station to those sectors in which capacityat any one time is needed. The baseband parts of the base station may bedivided among the different sectors of the base station. The radiofrequency block, of the We station, i.e. the transmitter/receiver unit,is capable of handling several carriers. In this manner, the number ofparts in the base station may be reduced, which consequently decreasesthe costs of constructing a network. The base station controls thetimeslot settings of the allocation means to be on and off so that atimeslot becoming free may be used by other terminals seeking to have aconnection. The solution according to the invention does not involvefixed allocation settings for the timeslots but the allocation settingsare changed dynamically.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

In the following, the invention will be described in more detail withreference to the examples in the accompanying drawings, in which

FIG. 1 illustrates the structure of the RX side of the base stationaccording to the invention,

FIG. 2 illustrates the structure of the TX side of the base stationaccording to the invention,

FIG. 3 illustrates the structure of the transmitter/receiver unit of thebase station according to the invention,

FIG. 4 illustrates how the allocation means and control means of thebase station according to the invention are connected to the basestation, and

FIG. 5 illustrates the structure of the cellular radio network accordingto the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows the receiving, i.e. RX, side of the base station of thecellular radio network. The receiving side consists of an antenna 11, agroup of transmitter/receiver units, i.e. RF units 12, and combined AIDconverter and demodulator parts 13. The receiving side further comprisesa first data bus 14 as well as filter parts 15 and baseband parts 16. Inthe case according to the figure, the signal received from the radiopath at the antenna 11 of the base station is connected via thetransmitter/receiver unit 12 to the combined AID converter and modulatorparts 13. The AID converter and, modulator parts 13 are connected viathe first data bus 14 to the filter parts 15 which are connected to thebaseband parts 16.

The radio frequency signal received from the radio path by the basestation of the cellular radio network first arrives at the antenna 11comprised by the base station. The cellular radio network consists of anumber of cells that are possibly divided into different sectors. Theterminals located in the sectors are within the coverage area of thebase station transmitting to the sector. In the solution of the figure,the base station antennas 11 receive a signal from different sectors. Ifterminals located within the same sector have a plurality of connectionsto other terminals, the base station antenna 11 handles a number ofdifferent carriers. The figure shows that the signal received by theantenna 11 is supplied in an antenna cable to the transmitter/receiverunit 12 in which an intermediate frequency signal, i.e. an IF signal, isformed from the signal. The IF signal comprises data comprised by anumber of different channels. The signal formed in thetransmitter/receiver unit 12 is applied further to the AND converter anddemodulator parts 13 in which the incoming analog signal is demodulatedand converted into digital form. The digital signal obtained is appliedvia the first data bus 14 to the channel-selective filter parts 15 inwhich disadvantageous features are filtered off from the digital signal.Following this, the filtered signal is applied to the baseband parts 16which performs various kinds of processings, such as decoding, for thesignal.

FIG. 2 shows the transmitting side, i.e. the TX side, of the basestation in the cellular radio system. The transmitting side comprises anantenna 21, transmitter/receiver units 22, D/A converter and modulatorparts 23, a first data bus 24 and baseband parts 25. The signal isconnected to the transmitting side of the base station according to thefigure first into the baseband parts 25 from which the signal isconnected via the first data bus 24 to the combined D/A converter andmodulator parts 23. From the D/A converter and modulator parts 23 thesignal is fed to the transmitter/receiver unit 22 and further, in anantenna cable, to the antenna 21 from which the signal is transmitted onthe radio path further to the terminals in the sector. In the solutionaccording to the invention, the base station comprises two antennas 21,both transmitting a signal to their respective sectors.

In the baseband parts 25 of the transmitting side of a base station in acellular radio network according to FIG. 2, various kinds of processingsare performed for the signal, including coding, multiplexing, andframing. The signal processed in the baseband parts 25 is supplied tothe first data bus 24 from which it is connected to the D/A converterand modulator parts 23. The D/A converter and modulator parts 23 choose,from the first data bus 24, a signal to be D/A converted and modulated.The analog signal received by the transmitter/receiver unit 22 from theD/A converter and modulator parts 23 comprises several modulatedfrequencies, that is, the signal contains data comprised by a number ofchannels. The signal is amplified in the transmitter/receiver parts 22,and the signal is fed in an antenna cable to the antenna 21 whichtransmits it to the radio path. The first data bus 24 enables the signalreceived from the baseband parts 23 to be sent to the radio path via anytransmitter/receiver unit 22 of the base station. The signal transmittedto the radio path is received by a terminal located in a sector of acell of the cellular radio network.

FIG. 3 illustrates the internal structure of the transmitter/receiverunit 12, 22 of the base station. The transmitter/receiver unit 12comprises, in the receiving direction, an RX amplifier 17, a localoscillator 19, a mixer 18 controlled by the local oscillator 19 and apassband filter 20. In the receiving direction, the signal received fromthe antenna 11 is applied to the amplifier 17 in which the signal thathas been attenuated on the radio path and in the antenna cable isamplified. The local oscillator 19 is connected to control the mixer 18.The mixer ;18 is used for shaping the signal received from the RXamplifier 17. The shaped signal is fed from the mixer 18 further to thepassband filter 19 in which the signal is filtered. In the filtering,e.g. signals which are off the receiving band and which do not containany important information are removed from the signal. The filteredsignal that is to be applied further to the AID converter 13 is referredto as an intermediate frequency signal, i.e. IF signal. The IF signal isa wideband signal, and it contains several channels channelled by theTime Domain Multiple Access (TDMA) method.

The transmitting direction of the transmitter/receiver 22 comprises a TXamplifier 27, a local oscillator 29 and a mixer 28. An analog signalcontaining a number of different frequencies is applied, in thetransmission direction, from the modulator and D/A converter 23 to thetransmitter/receiver Unit 22. The signal is applied to the mixer 28controlled by the local oscillator 29, in which the signal is used formodulating the carrier. The signal obtained from the mixer 28 is furtherapplied to the TX amplifier 27 in which the signal is amplified. Theamplified signal is then applied in an antenna cable to the antenna 21and further to be transmitted to a terminal located in a sector of acell in the cellular radio network. The transmitter/receiver unit 22 iscapable of handling several carriers.

FIG. 4 shows a block diagram of a base station comprising a first databus 24, and D/A converter and modulator parts 23 as well as basebandparts 25 connected via it. In addition, the base station comprises asecond data bus 26 and allocation means 31 connected via it to thebaseband parts 25. In the base station solution set forth, one set ofbaseband parts 25 is able to handle channels comprised in one carrier,of which there are usually eight. A carrier may also have more channels.For example, if the base station operates in a half rate mode thecarrier transmitted may have 16 channels. The allocation means 31according to the figure receive signals e.g. from a PSTN network (PublicService Telephone Network) which utilizes e.g. PCM technique (PCM=PulseCode Modulation). The input signals to the allocation means 31 may alsooriginate e.g. from a Base Station Controller (i.e. BSC).

In the block diagram set forth, the baseband parts 25 constitute a pool,i.e. a group in which the channels passing through the baseband parts 25may be connected freely to any sector of the base station. In thismanner it is possible to reduce the number of parts in the base station,which results in lower costs. What was described above means that thebase station employs an efficient joint use of radio channels. In jointuse of channels, not all the channels of the different sectors are usedsimultaneously. This means that the capacity of the channels may easilybe divided among a plurality of users. In the solution according to theinvention, the transmitter/receiver unit 22 handles a number ofcarriers, which makes further simplifications possible in the basestation structure, particularly if the method of the invention forallocating timeslots is in use. In the preferred case, the sector needsjust one transmitter/receiver unit 22 which handles all the carriers tobe transmitted to the sector.

In the solution according to FIG. 4, the base station controls thechannel allocation taking place in the allocation means 31. The basestation a comprises control means 32 for assigning the channels receivedat the allocation means 31 to different carriers. As the solutionaccording to the invention enables the base station to define anadvantageous position at any one time for the timeslots in the carrierto be transmitted, a most flexible base station solution may beobtained. There is no need for predetermined allocation settings, as theallocation means 31, controlled by the control means 32 of the basestation, allocate the channels to the correct sectors. Thus, thetimeslots, or channels therein, received by the baseband parts 25 of thebase station may be arranged freely to any carrier or sector.

FIG. 5 shows a cellular radio network comprising two cells, 80 and 81.The cell 80 comprises a base station 100. The cell 80 has been dividedinto four sectors 51-54. In the case illustrated by the figure, the basestation 100 comprises four antennas 61-64, each directed towards theirrespective sectors 51-54. The sectors 51-54 constitute the coverage areafor the base station 100 In the solution of the figure, the sectors51-54 comprise a group of terminals 41-44 within their area. Inaddition, the base station 100 comprises control means 32 and allocationmeans 31.

The cell 81 also comprises a base station 200. Instead, the base station200 only comprises one antenna 65 directed towards the sector 55. Thesector 55 also contains a group of terminals 45 within the coverage areaof the base station 200. The base station I 00 and the base station 200are interconnected e.g. by a PSTN network 70. A signal 70 received bythe allocation means 31 of the base station 100, 200 may also originatee.g. from the base station controller.

The base station 100 of the cellular radio network illustrated in FIG. 5utilizes the solution according to the invention. The antennas 61-64comprised by the base station 100 each transmit and receive a signalfrom their respective sectors 51-54. To each antenna 61-64 of the basestation 100, transmitter/receiver units 12, 22 comprised by the basestation 100 have been connected which are used for transmitting andreceiving carriers. The cellular radio network additionally comprises ineach sector 51-54, i.e. within the coverage area of the base station,terminals 41-44 the number of which is not stable but varies with time.The terminals 41-44 communicate via the base station 100 with theterminals 45 located e.g. in the sector 55 of the cell 81.

To facilitate understanding the point, it is assumed that in thesolution according to FIG. 5 there are at first eight terminals 41-44 ineach sector 51-54 of the cell 80, the terminals communicating e.g. withterminals 45 that are in the sector 55 of the cell 81. In the basestation 100 according to the figure, each transmitter/receiver unit 12,22 at first only transmits one carrier to each sector 51-54, whereby thecarriers being transmitted have no capacity left to transmit morechannels. The control means 32 in the base station 100 control thetimeslot settings of the allocation means 31 so that the base station100 assigns the terminals 41-44 in the sectors 51-54 with more timeslotsto use if the need arises. If additional capacity is required, thecontrol means 32 also instruct the base station 100 to take in use asufficient number of carriers in which the channels required by theadditional capacity may be transmitted. If the terminals 41-44 in thesectors 51-54 cut off their connections the allocation means 31 in thebase station 100 release, under control of the control means 32, thetimeslots earlier temporarily allocated for the duration of theconnection by e.g. the terminals 41-44. At the same time, transmissionof carriers not required any longer is discontinued. Hence, theallocation means 31 have no fixed timeslot settings. Upon changes in thenumber of connections by terminals 41-44 that are in the coverage areaof the base station 100, i.e. in sectors 51-54, the base station 100 isinformed of the changed situation and, by employing the control means32, the base station 100 controls the allocation means 31 according tothe changed situation.

Referring to FIG. 5 it is further assumed that there are eight terminals41 in the sector 51 of the cellular radio network, communicating withthe terminals 45 in the coverage area 55 of the base station 200. Theterminals 41 within the sector 51 use timeslots TS1-TS8 (TS=Time Slot)in the signal 70 to the base station. Each timeslot is able to carry onechannel between terminals 41 in the sector 51 and terminals 45 in thesector 55. When one of the terminals 41 cuts off a connection, theallocation means 31 release controlled by the control means 32, thetimeslot settings of the terminal 41 in question. If all the terminals41 within the cell 51 area cut off their connections, the timeslotsTS1-TS8 may again be reserved by the terminals 41-44 in the sectors51-54. If, for example, the carrier transmitted to the sector 52 has allits channels in use, the sector 52 may, controlled by the control means32 of the base station 100, have more carriers to use in which thechannels may be sent forward e.g. in the timeslots TS1-TS8 that werereleased above. Therefore, fixed and inflexible timeslot setting can beavoided. By the solution according to the invention, the network willnot be blocked even in case of great changes in the load.

Although the invention is in the above described with reference to theexample in the accompanying drawings, it is obvious that the inventionis not restricted thereto but may be modified in many ways within theinventive idea of the attached claims.

What is claimed is:
 1. A method for controlling abase station used in acellular radio system employing TDMA multiple access techniques andincluding terminals, sectors and at least one base station whichtransmits one or more carriers, wherein the base station includes aplurality of baseband parts, and at least one transceiver unit, which iscoupled to the rest of the system by a digital transmission lineconfigured to transmit information in the timeslots, the methodcomprising: dynamically allocating the timeslots as required todifferent carriers, dynamically allocating the baseband parts asrequired to different sectors, wherein a timeslot dynamically allocatedto a carrier passes through a dynamically allocated baseband part, andwherein the dynamically allocated baseband part through which thetimeslot passes may be freely associated with different sectors.
 2. Themethod of claim 1, wherein one transceiver unit handles a plurality ofcarriers.
 3. The method of claim 1, wherein one transceiver unit handlesall the carriers sent to the same sector.
 4. The method of claim 1,wherein the timeslots are allocated to different carriers so that onecarrier will have no more than 16 timeslots.
 5. A method for controllinga base station used in a cellular radio system employing TDMA multipleaccess method and comprising terminals, and at least one base stationwhich transmits one or more carriers, and which comprises a number ofbaseband parts, and at least one transmitter/receiver unit, and which isconnected to the rest of the system by a digital transmission line inwhich information is transmitted in timeslots, the method comprising:the timeslots are allocated as required to different carriers, thebaseband parts are allocated as required to different sectors, and thebaseband parts are allocated so that timeslots routed via the samebaseband part are transmitted to different sectors.
 6. A base stationused in a cellular radio system employing TDMA multiple accesstechniques and including terminals, sectors, a digital transmissionline, and at least one base station which transmits one or morecarriers, the base station including a plurality of baseband parts, andleast one transceiver, which is coupled to the rest of the system by thedigital transmission line configured to transmit information intimeslots, the base station comprising: control means for dynamicallyallocating the timeslots as required to different carriers, and fordynamically allocating the baseband parts to the different sectors,wherein a timeslot dynamically allocated to a carrier passes through adynamically allocated baseband part, and wherein the dynamicallyallocated baseband part through which the timeslot passes may be freelyassociated with different sectors.
 7. The base station of claim 6,wherein the transceiver unit is arranged to handle a plurality ofcarriers.
 8. The base station of claim 6, wherein the transceiver unitis arranged to handle all the channels transmitted in one carrier. 9.The base station of claim 6, wherein the control means control theallocation of timeslots to different carriers so that one carrier willcontain no more than 16 timeslots.
 10. A base station used in a cellularradio system employing TDMA multiple access method and includingterminals, sectors, a transmission line and at least one base stationwhich transmits one or more carriers, and which comprises a number ofbaseband parts, and at least one transmitter-receiver, which isconnected to the rest of the system by a digital transmission line inwhich information is transmitted in timeslots, the base stationcomprising: control means for allocating the timeslots as required todifferent carriers, and for allocating the baseband parts to differentsectors, and wherein the baseband parts are arranged to be allocated sothat timeslots routed via the same baseband part are transmitted to thedifferent sectors.
 11. A base station used in a cellular radio systememploying TDMA multiple access method and comprising terminals, sectors,a transmission line and at least one base station which transmits one ormore carriers, and which comprises a number of baseband parts, and atleast one transmitter-receiver, which is connected to the rest of thesystem by a digital transmission line in which information istransmitted in timeslots, the base station comprising: control means forallocating the timeslots as required to different carriers, and forallocating the baseband parts to different sectors, and wherein the basestation further comprises allocation means controlled by the controlmeans for allocating the timeslots, and wherein the allocation means arearranged to allocate the timeslots to different baseband parts.
 12. Amethod for controlling a base station used in a cellular radio systememploying TDMA multiple access techniques and including terminals,sectors and at least one base station which transmits one or morecarriers, wherein the base station includes a plurality of basebandparts, and at least one transceiver unit, which is coupled to the restof the system by a digital transmission line configured to transmitinformation in the timeslots, the method comprising: allocating thetimeslots as required to different carriers, dynamically allocating thebaseband parts as required to different sectors, and allocating thebaseband parts so that timeslots routed via the same baseband part aretransmitted to different sectors.
 13. A base station used in a cellularradio system employing TDMA multiple access techniques and includingterminals, sectors, a transmission line and at least one base stationwhich transmits one or more carriers, wherein the base station includesa plurality of baseband parts, and least one transmitter-receiver, whichis connected to the rest of the system by a digital transmission lineconfigured to transmit information in the timeslots, the base stationcomprising: control means for allocating the timeslots as required todifferent carriers, and for allocating the baseband parts to differentsectors, and wherein the baseband parts are arranged to be allocated sothat timeslots routed via the same baseband part are transmitted to thedifferent sectors.
 14. A base station used in a cellular radio systememploying TDMA multiple access techniques and including terminals,sectors, a transmission line and at least one base station whichtransmits one or more carriers, wherein the base station includes aplurality of baseband parts, and least one transmitter-receiver, whichis connected to the rest of the system by a digital transmission lineconfigured to transmit information in the timeslots, the base stationcomprising: control means for allocating the timeslots as required todifferent carriers, and for allocating the baseband parts to differentsectors, and wherein the base station further comprises allocation meanscontrolled by the control means for allocating the timeslots, andwherein the allocation means are arranged to allocate the timeslots todifferent baseband parts.